In systems that transmit microwave signals, such as communication systems and radar systems, it is desirable to know the amount of energy being transmitted. Typically, power detectors are used to convert a microwave transmit signal to a voltage that represents that signal's energy level. These RF power detector circuits typically include a detector element, such as a detector diode, that is very non-linear with respect to the power level. The nonlinearity that results reduces the dynamic range of the power detector and results in a lower sensitivity for the power detector. Furthermore, these power detectors also, in general, tend to vary over temperature because of the temperature characteristics of the detector element. As a result, typical power detectors provide different output voltages for the same power level at different temperatures. In the radar and communication systems, the use of these typical RF detector circuits results in a voltage that is not necessarily representative of the output power transmitted. This problem is especially pronounced at high microwave frequencies, such as K-Band and other millimeter wave frequencies where it is especially important to conserve the amount of energy being used to transmit signals. Furthermore, any source of variation may cause substantial error in the transfer characteristics of such circuits.
Accordingly, what is needed is an RF power detector circuit that provides an increased dynamic range. What is also needed is an RF power detector circuit with higher sensitivity. What is also needed is an power detector circuit with improved temperature stability. What is also needed is a method and apparatus for providing power detection at microwave and millimeter wave frequencies with a higher dynamic range. What is also needed is a power detection apparatus with higher sensitivity and improved temperature stability. What is also needed is an RF power detector apparatus that compensates for the nonlinearities of the detector element suitable for use in a communication or radar system.